The Chasam Sofer would always admonish his disciples never to pose a difficult question to a stranger or a person they knew might not know the answer. This is because it could embarrass him or and that is an aveirah for which a person can lose their share in the World to Come.
He cited the following story which took place while he was traveling in the company of an elderly gentleman whose majestic figure, long, well-kept beard, immaculate gabardine and proud bearing gave him a scholarly appearance. This man’s education, however, had been woefully neglected, and he was completely ignorant of the Torah.
They stopped off in a small town and entered the local shul where they came upon a group of Talmudic students who were discussing a difficult passage in the Talmud. Seeing the scholarly-looking gentleman, the quieted down.
“Let us ask that gentleman to explain this difficult passage to us,” they said to one another.
In a moment, the patriarchal gentleman was surrounded by a score of eager students, who set forth their opinions as the exact meaning of the noted passage and entreated him to kindly tell them what the right interpretation was.
The bearded gentleman, although ignorant of the Torah, was a very wily person and not at all disconcerted. With a reproachful look in his eyes, he addressed the young students as follows:
“Look here, my children,” he said. “I think you have very bad manners. Fortunately, you happened to approach a lamdan who is in a position to answer you. But suppose you asked this question of an untutored man, you surely would have embarrassed him. Therefore, I am not going to tell you the answers to these questions, just to teach you a lesson in manners.”